The fabrication of integrated circuits (ICs) involves the formation of features on a substrate that make up circuit components, such as transistors, resistors and capacitors. The devices are interconnected, enabling the ICs to perform the desired functions. An important aspect of the manufacturing of ICs is the need to provide planar surfaces using chemical mechanical polishing (CMP).
CMP tools generally include a platen with a polishing pad. A wafer carrier including a polishing head is provided. The polishing head holds the wafer so that the wafer surface that is to be polished faces the polishing pad. During polishing, the polishing head presses the wafer surface against a rotating polishing pad. A retaining ring holds the wafer in place by centering the wafer on the polishing pad and preventing the wafer from slipping laterally. During the CMP process, material is not only removed from the surface of the wafer to be planarized, but also from the polishing side surface of the retaining ring. This results in the decrease in the depth of grooves that are present on the side surface of the retaining ring, which could result in non-uniformity in the CMP process. As such, the retaining ring may need to be replaced frequently to maintain the desired uniformity.
As the polishing tool has to be taken offline when replacing the retaining ring, it could become quite costly to replace the retaining ring. Hence, there is a need for a CMP method and apparatus that could prolong the life of the retaining ring thereby reducing the cost of semiconductor processing.